Semiconductor device, and method of forming the same

ABSTRACT

In order to realize a semiconductor device of enhanced TFT characteristics, a semiconductor thin film is selectively irradiated with a laser beam at the step of crystallizing the semiconductor thin film by the irradiation with the laser beam. By way of example, only driver regions ( 103  in FIG.  1 ) are irradiated with the laser beam in a method of fabricating a display device of active matrix type. Thus, it is permitted to obtain the display device (such as liquid crystal display device or EL display device) of high reliability as comprises the driver regions ( 103 ) made of crystalline semiconductor films, and a pixel region ( 102 ) made of an amorphous semiconductor film.

This is a divisional of copending U.S. application Ser. No. 09/500,125,filed on Feb. 8, 2000 now U.S. Pat. No. 6,506,635.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device having a circuitwhich is configured of thin film transistors (hereinbelow, oftenabbreviated to “TFT”). By way of example, it relates to theconstructions of an electrooptic device which is typified by a liquidcrystal display panel, and an electronic equipment in which such anelectrooptic device is installed as a component.

Incidentally, here in this specification, the expression “semiconductordevice” is intended to signify general devices which can function byutilizing semiconductor properties, and it shall cover all ofelectrooptic devices, semiconductor circuits and electronic equipmentwithin its category.

2. Description of the Related Art

In recent years, notice has been taken of technology wherein thin filmtransistors (TFTs) are constructed using a semiconductor thin film(several to a few hundred [nm] thick) which is formed on a substratehaving an insulating surface. The TFTs are extensively applied to ICs(integrated circuits) and electronic devices such as electroopticdevices, and it is especially hurried to develop them as the switchingelements of an image display device.

In, for example, a liquid crystal display device, attempts have beenmade to apply TFTs to all sorts of electric circuits such as a pixelunit in which pixels arrayed in the shape of a matrix are individuallycontrolled, a driver circuit which controls the pixel unit, and a logiccircuit (including a processor circuit, a memory circuit, etc.) whichprocesses data signals fed from outside.

Besides, there has been known a construction (system-on-panel) in whichthe above circuits (pixel unit, driver circuit, etc.) are packaged on asingle substrate. In the pixel unit, the pixel plays the role ofretaining information sent from the driver circuit. Herein, unless theOFF current of the TFT connected to the pixel is sufficiently small, theinformation cannot be retained, and a good display cannot be presented.

On the other hand, in the driver circuit, a high mobility is required ofthe TFTs. As the mobility is higher, the structure of this circuit canbe simplified more, and the display device can be operated at a higherspeed.

As stated above, the TFTs arranged in the driver circuit and thosearranged in the pixel unit are different in the required properties.More specifically, the TFTs arranged in the pixel unit need not have avery high mobility, but their requisites are that the OFF current issmall and that the value thereof is uniform throughout the pixel unit.In contrast, the TFTs of the driver circuit located around the pixelunit take preference of the mobility over the OFF current, and theirrequisite is that the mobility is high.

It has been difficult, however, to manufacture the TFTs of thepreferential mobility and the TFTs of the small OFF current on anidentical substrate at a high productivity and without spoiling theirreliabilities, by employing a fabricating method in the prior art.

SUMMARY OF THE INVENTION

As understood from the foregoing, a quite new construction havinghitherto been nonexistent is required in order to incarnate asystem-on-panel which has a built-in logic circuit.

In compliance with such a requirement, the present invention has for itsobject to provide an electrooptic device represented by AM-LCD(Active-Matrix Liquid Crystal Display), the respective circuits of whichare formed using TFTs of appropriate structures in accordance with theirfunctions, and which is accordingly endowed with a high reliability.

The construction of the present invention disclosed in thisspecification consists in a semiconductor device having a driver circuitand a pixel unit which are formed on an identical substrate,characterized in:

-   -   that a channel forming region of at least one TFT (thin film        transistor) included in said driver circuit is made of a        crystalline semiconductor film; and    -   that a channel forming region of a TFT included in said pixel        unit is made of an amorphous semiconductor film.

Besides, in the above construction, the semiconductor device ischaracterized in that said channel forming region of said at least oneTFT included in said driver circuit is formed via a processing step ofirradiation with a laser beam or an intense light beam similar thereto.

Also, in the above construction, the semiconductor device ischaracterized in that the channel forming regions of said at least oneTFT included in said driver circuit and said TFT included in said pixelunit are made of a semiconductor film which is formed by sputtering.

Further, in the above construction, the semiconductor device ischaracterized in that gate insulating films of said at least one TFTincluded in said driver circuit and said TFT included in said pixel unitare made of an insulating film which is formed by sputtering.

Still further, in the above construction, the semiconductor device ischaracterized in that said crystalline semiconductor film is ofpolysilicon, while said amorphous semiconductor film is of amorphoussilicon.

Yet further, in the above construction, the semiconductor device ischaracterized by being a display device of active matrix type, forexample, an EL (electroluminescent) display device or a liquid crystaldisplay device.

In addition, the construction of the present invention for realizing theabove structure consists in:

-   -   a method of fabricating a semiconductor device having a driver        circuit and a pixel unit which are formed on an identical        substrate, characterized by comprising:        -   the first step of forming an amorphous semiconductor film on            an insulating surface of said substrate;        -   the second step of irradiating a selected part of said            amorphous semiconductor film with either of a laser beam and            an intense light beam similar thereto, thereby to turn the            part of said amorphous semiconductor film into a crystalline            semiconductor film;        -   the third step of patterning said crystalline semiconductor            film, thereby to form a semiconductor layer of said driver            circuit, and also patterning the resulting amorphous            semiconductor film, thereby to form a semiconductor layer of            said pixel unit;        -   the fourth step of forming an insulating film on the            semiconductor layers; and        -   the fifth step of forming gate electrodes on said insulating            film.

Besides, in the above construction, the fabricating method ischaracterized in that said fourth step is implemented by sputtering.

Another construction of the present invention consists in:

-   -   a method of fabricating a semiconductor device having a driver        circuit and a pixel unit which are formed on an identical        substrate, characterized by comprising:        -   the first step of forming an amorphous semiconductor film on            an insulating surface of said substrate;        -   the second step of forming an insulating film on said            amorphous semiconductor film;        -   the third step of irradiating a selected part of said            amorphous semiconductor film with either of a laser beam and            an intense light beam similar thereto through said            insulating film, thereby to turn the part of said amorphous            semiconductor film into a crystalline semiconductor film;        -   the fourth step of patterning said crystalline semiconductor            film, thereby to form a semiconductor layer of said driver            circuit, and also patterning the resulting amorphous            semiconductor film, thereby to form a semiconductor layer of            said pixel unit; and        -   the fifth step of forming gate electrodes on said insulating            film.

Besides, in the above construction concerning the fabrication, thefabricating method is characterized in that said second step isimplemented by sputtering.

Also, in each of the above constructions concerning the fabrication, thefabricating method is characterized in that said first step isimplemented by sputtering.

Still another construction of the present invention consists in:

-   -   a method of fabricating a semiconductor device having a driver        circuit and a pixel unit which are formed on an identical        substrate, characterized by comprising:        -   the first step of forming gate electrodes on an insulating            surface of said substrate;        -   the second step of forming an insulating film on said gate            electrodes;        -   the third step of forming an amorphous semiconductor film on            said insulating film;        -   the fourth step of irradiating a selected part of said            amorphous semiconductor film with either of a laser beam and            an intense light beam similar thereto, thereby to turn the            part of said amorphous semiconductor film into a crystalline            semiconductor film; and        -   the fifth step of patterning said crystalline semiconductor            film, thereby to form a semiconductor layer of said driver            circuit, and also patterning the resulting amorphous            semiconductor film, thereby to form a semiconductor layer of            said pixel unit.

Besides, in each of the constructions concerning the fabrication, thefabricating method is characterized by comprising after said fifth step:

-   -   the sixth step of doping selected regions to become source and        drain regions, with elements which belong to the 15th Group and        13th Group of elements; and    -   the seventh step of activating said elements which belong to        said 15th Group and 13th Group, and with which the semiconductor        layers have been doped.

Also, in each of the constructions concerning the fabrication, thefabricating method is characterized in that said semiconductor device isa liquid crystal display device.

Further, in each of the constructions concerning the fabrication, thefabricating method is characterized by comprising after said seventhstep of activating said elements:

-   -   the eighth step of forming an interlayer insulating film over        the active layers;    -   the ninth step of forming a pixel electrode on said interlayer        insulating film;    -   the tenth step of forming an EL layer on said pixel electrode;        and    -   the eleventh step of forming either of a cathode and an anode on        said EL layer.

Still further, in each of the above constructions concerning thefabrication, the fabricating method is characterized in that saidsemiconductor device is an EL display device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an optical arrangement diagram showing a laser irradiationmethod in the present invention;

FIGS. 2(A) thru 2(D) are sectional views showing the steps of a processfor fabricating an AM-LCD (active-matrix liquid crystal display);

FIGS. 3(A) thru 3(D) are sectional views showing the steps of theprocess for fabricating the AM-LCD;

FIGS. 4(A) thru 4(C) are sectional views showing the steps of theprocess for fabricating the AM-LCD;

FIGS. 5(A) and 5(B) are a block diagram showing the circuit arrangementof the AM-LCD, and a top plan view showing a pixel unit in the AM-LCD,respectively;

FIG. 6 is an optical arrangement diagram showing a laser irradiationmethod in the present invention;

FIGS. 7(A) thru 7(C) are sectional views showing the steps of a processfor fabricating an AM-LCD;

FIGS. 8(A) thru 8(D) are sectional views showing the steps of theprocess for fabricating the AM-LCD;

FIGS. 9(A) thru 9(C) are sectional views showing the steps of theprocess for fabricating the AM-LCD;

FIGS. 10(A) and 10(B) are top plan views each showing a CMOS(complementary metal-oxide-semiconductor transistor) circuit;

FIG. 11 is a perspective view showing the external appearance of anAM-LCD;

FIG. 12 is a circuit diagram showing an active matrix type EL(electroluminescent) display device;

FIGS. 13(A) and 13(B) are a top plan view and a sectional view showingthe active matrix type EL display device, respectively;

FIGS. 14(A) thru 14(F) are schematic views each showing an example ofelectronic equipment; and

FIGS. 15(A) thru 15(C) are schematic views each showing an example ofelectronic equipment.

DETAILED DESCRIPTION OF THE INVENTION

The aspects of performance of the present invention will be describedbelow. It features the present invention that an amorphous semiconductorfilm and a crystalline semiconductor film are separately employed as theactive layers of the TFTs of those circuits of an electrooptic device,represented by AM-LCD (Active-Matrix Liquid Crystal Display) or EL(electroluminescent) display device, which are formed on an identicalsubstrate, in accordance with the functions of the circuits. By way ofexample, in the electrooptic device represented by the AM-LCD or the ELdisplay device, it is the feature of the present invention that theamorphous semiconductor film (such as amorphous silicon film) is used asthe active layers of the TFTs arranged in a pixel unit, whereas thecrystalline semiconductor film (such as polysilicon film orpolycrystalline silicon film) is utilized as the active layers of theTFTs arranged in an electric circuit required to be capable of operatingat high speed, such as driver circuit or logic circuit.

For the purpose of incarnating the above construction, the amorphoussemiconductor film needs to be selectively crystallized into thecrystalline semiconductor film on the identical substrate. Such a methodof forming the crystalline semiconductor film is also the feature of thepresent invention.

An example of the forming method according to the present invention willbe described with reference to FIG. 1. This figure is a schematicdiagram showing the example in the case where only the amorphoussemiconductor film of each driver circuit 103 formed on a substrate 101are irradiated with the beam of a pulsed laser such as excimer laser.

Referring to FIG. 1, the substrate 101 is a refractory one, which may bea glass substrate, a quartz substrate, a silicon substrate, a ceramicssubstrate, or a metal substrate (typically, stainless steel substrate).In case of employing any of the substrates, a base film (preferably, aninsulating film whose main component is silicon) may well be provided ifnecessary. Although not shown, an amorphous semiconductor film formed bysputtering is provided on the substrate 101. Accordingly, definiteboundaries cannot be actually seen with the eye at this stage, but apixel unit 102 and the driver circuits 103 to be formed later areillustrated for the sake of convenience.

The laser beam emitted from the excimer-laser light source 105 has itsbeam shape, energy density, etc. regulated by an optical system (beamhomogenizers 106, a mirror 107, etc.), thereby to define a laser spot108. Besides, an X-Y stage 104 to which the substrate 101 is fixed ismoved in an X-direction or a Y-direction, whereby only the amorphoussemiconductor film of each driver circuit 103 is irradiated with thelaser spot 108 in the laser spot scanning direction 109. However, aperson who controls the fabricating method should properly determine theconditions of the laser beam, etc. (the irradiating intensity of thelaser beam, the pulse width thereof, the pulse repetition frequencythereof, the time period of the irradiation, the temperature of thesubstrate, the moving speed of the stage, the overlap ratio of scannedareas, etc.) in consideration of the thickness of the amorphoussemiconductor film, etc. Here, in a case where the laser beam has leakedto irradiate the pixel unit 102, dispersion arises in thecharacteristics of the TFTs. It is therefore important to arrange theoptical system so that the laser beam may not leak. In addition, thespacing X between the driver circuit 103 and the pixel unit 102 needs tobe properly set.

When the laser irradiation method illustrated in FIG. 1 is employed, itis permitted to irradiate only the driver circuits 103 with the laserbeam, and the selected parts of the amorphous silicon film can becrystallized.

Besides, apart from the pulsed laser such as excimer laser, a continuouswave laser such as argon laser, a continuous-emission excimer laser, orthe like can be employed as the light source of the laser beam.

It is also allowed to employ a process in which the irradiation with thelaser beam is implemented after the formation of an insulating film onthe amorphous semiconductor film.

FIG. 6 illustrates an example in the case where the amorphoussemiconductor film of each driver circuit 603 is irradiated with thebeam of a continuous wave laser such as argon laser 605. Referring tothe figure, numeral 601 designates a substrate, numeral 606 a beamexpander, numeral 607 a galvanometer, and numeral 604 a one-axisoperation stage. Although not shown, an amorphous semiconductor filmbased on sputtering is provided on the substrate 601.

The laser beam emitted from the argon-laser light source 605 has itsbeam shape, energy density, etc. regulated by an optical system (thebeam expander 606, the galvanometer 607, an f-θ (flyeye) lens 608,etc.), thereby to define a laser spot 609. Besides, the laser spot 609is vibrated in directions parallel to a laser spot scanning direction610 by vibrating the galvanometer 607, while at the same time, theone-axis operation stage 604 to which the substrate 601 is fixed ismoved step by step (the interval of the steps being nearly equal to thediameter of the laser spot 609) in one direction (the operatingdirection 611 of the one-axis operation stage 604). Thus, only theamorphous semiconductor film of each driver circuit 603 is crystallized.As in the case of the laser irradiation method illustrated in FIG. 1, itis important to arrange the optical system so that the laser beam maynot leak to irradiate a pixel unit 602.

When the laser irradiation method illustrated in FIG. 6 is employed, itis permitted to irradiate only the driver circuits 603 with the laserbeam, and the selected parts of the amorphous silicon film can becrystallized, in the same manner as in the laser irradiation methodillustrated in FIG. 1.

In addition to the construction of FIG. 1 or FIG. 6, a resist mask basedon an ordinary photolithographic process may well be formed on thesubstrate so as to prevent the laser beam from leaking and irradiatingthe pixel unit. Alternatively, a photo-mask may well be employed.

Besides, although the example of defining the laser spot has beenmentioned in FIG. 1 or FIG. 6, the present invention is not especiallyrestricted thereto. It is also allowed to adopt a construction in whichthe selected parts of the amorphous semiconductor film are irradiatedwith a linear laser beam by using a mask. Alternatively, a large-areaspot laser represented by “Sopra” may well be worked into the size ofeach driver circuit so as to implement a process for crystallizing allthe amorphous semiconductor region of the driver circuit at once.

Shown in FIG. 4(C) is the sectional view of an AM-LCD in which drivercircuits and a pixel unit are unitarily formed on an identical substrateby utilizing the laser-beam irradiation method of the present invention.By the way, a CMOS (complementary metal-oxide-semiconductor transistor)circuit is illustrated here as a basic circuit constituting each drivercircuit, and a TFT of double-gate structure as the TFT of the pixelunit. Of course, the double-gate structure is not restrictive at all,but it may well be replaced with any of a triple-gate structure, asingle-gate structure, etc.

Numeral 202 designates a silicon oxide film which is provided as a basefilm, and which is overlaid with the active layers of the TFTs of thedriver circuit, the active layer of the TFT of the pixel unit, and asemiconductor layer to serve as the lower electrode of a retentioncapacitance. Here in this specification, an expression “electrode”signifies a portion which is part of a “wiring line” and at which thewiring line is electrically connected with another wiring line, or aportion at which the wiring line intersects with a semiconductor layer.Accordingly, although the expressions “wiring line” and “electrode” willbe separately used for the sake of convenience, the word “electrode”shall be always implied in the expression “wiring line”.

Referring to FIG. 4(C), the active layers of the. TFTs of the drivercircuit include the source region 221, drain region 220, LDD(lightly-doped drain) regions 228 and channel forming region 209 of theN-channel TFT (hereinbelow, shortly termed “NTFT”), and the sourceregion 215, drain region 216 and channel forming region 217 of theP-channel TFT (hereinbelow, shortly termed “PTFT”).

Besides, the active layer of the TFT (as which an NTFT is employed here)of the pixel unit includes the source region 222, drain region 224, LDDregions 229 and channel forming regions 212 thereof. Further, asemiconductor layer extended from the drain region 224 is used as thelower electrode 226 of the retention capacitance.

Incidentally, although the lower electrode 226 is directly connectedwith the drain region 224 of the TFT of the pixel unit in the case ofFIG. 4(C), the lower electrode 226 and the drain region 224 may well beindirectly connected into a structure in which they lie in electricalconnection.

The semiconductor layer as the lower electrode 226 is doped with anelement which belongs to the 15th Group of elements. That is, even whenany voltage is not applied to the upper wiring line 206 f of theretention capacitance, the lower electrode 226 can be directly used assuch. Therefore, the doping with the element is effective fordiminishing the power consumption of the AM-LCD.

Besides, it is one of the features of the present invention that thechannel forming regions 212 of the TFT of the pixel unit aresemiconductor films in an amorphous state, whereas the channel formingregions 209, 217 of the TFTs of the driver circuit are crystallinesemiconductor films having crystallinity.

It is also one of the features of the present invention that the channelforming regions 209, 212, 217 of the respective TFTs are semiconductorfilms which are formed by sputtering, and whose hydrogen concentrationsare low. The semiconductor film formed by the sputtering exhibits thehydrogen concentration which is at least one order lower as comparedwith that of a semiconductor film formed by plasma CVD (chemical vapordeposition). Accordingly, the film formed by the sputtering can befollowed by laser crystallization without performing a dehydrogenatingtreatment. In contrast, a process employing the plasma CVD has beendemeritorious from the viewpoint of the safety of a job environmentbecause of being highly liable to explosion. The present inventionfeatures that thin films, such as amorphous semiconductor films(amorphous silicon films, etc.), insulating films and conductor layers,are formed by the sputtering in order to take preference of the safetyand productivity of fabrication. More preferably, the films areconsecutively formed to the utmost in order to prevent them from beingcontaminated due to the atmospheric air.

Here, the gate insulating films of the respective TFTs are formed of anidentical insulating film 205 of uniform thickness, but this is notespecially restrictive. By way of example, at least two sorts of TFTswhose gate insulating films are formed of different insulating films maywell exist on an identical substrate in accordance with circuitcharacteristics. Incidentally, when the semiconductor film and the gateinsulating film are consecutively formed using the sputtering, favorablya good interface is obtained between them.

Subsequently, the gate wiring line 206 d of the TFT of the drivercircuit and the gate wiring line 206 e of the TFT of the pixel unit areformed on the gate insulating film 205. Simultaneously, the upperelectrode 206 f of the retention capacitance is formed over the lowerelectrode 226 thereof through the gate insulating film 205.

The materials of the wiring lines in the present invention typicallyinclude conductive silicon films (for example, a phosphorus-dopedsilicon film and a boron-doped silicon film), and metal films (forexample, a tungsten film, a tantalum film, a molybdenum film, a titaniumfilm, an aluminum film and a copper film). They may well be silicidefilms produced by silicifying the metal films, and nitride filmsproduced by nitrifying the metal films (a tantalum nitride film, atungsten nitride film, a titanium nitride film, etc.). Moreover, thematerials may well be combined and stacked at will.

Besides, in the case of employing any of the metal films, a structure inwhich the metal film is stacked with a silicon film is desirable for thepurpose of preventing the oxidation of the metal film. In addition, astructure in which the metal film is covered with a silicon nitride filmis effective in the sense of the prevention of the oxidation.

Next, numeral 230 indicates a first interlayer insulating film, which isformed of an insulating film (single layer or stacked layer) containingsilicon. Any of a silicon oxide film, a silicon nitride film, anoxidized silicon nitride film (which contains nitrogen more thanoxygen), and a nitrified silicon oxide film (which contains oxygen morethan nitrogen) can be used as the insulating film which contains theelement silicon.

Besides, the first interlayer insulating film 230 is provided withcontact holes so as to form the source wiring lines 231, 233 and drainwiring line 232 of the TFTs of the driver circuit and the source wiringline 234 and drain wiring line 235 of the TFT of the pixel unit. Apassivation film 236 and a second interlayer insulating film 237 areformed on the first interlayer insulating film 230 as well as the wiringlines 231-235. After the films 236, 237 have been provided with acontact hole, a pixel electrode 238 is formed.

Incidentally, a black mask (light shield film) is not formed in theexample of FIG. 4(C). However, this is not especially restrictive, butthe black mask may be formed as is needed. It is also allowed to employ,for example, a construction in which a counter substrate is providedwith a light shield film, or a construction in which each TFT isunderlaid or overlaid with a light shield film made of the same materialas that of the gate wiring line.

A resin film of low relative permittivity is favorable as the secondinterlayer insulating film 237. Usable as the resin film is a polyimidefilm, an acrylic resin film, a polyamide film, a BCB (benzocyclobutene)film, or the like.

In addition, a transparent conductive film represented by an ITO (indiumtin oxide) film may be used as the pixel electrode 238 in case offabricating a transmission type AM-LCD, while a metal film of highreflectivity represented by an aluminum film may be used in case offabricating a reflection type AM-LCD.

By the way, although the pixel electrode 238 is electrically connectedwith the drain region 224 of the TFT of the pixel unit through the drainelectrode 235 in the structure of FIG. 4(C), this structure may well bereplaced with a structure in which the pixel electrode 238 and the drainregion 224 are directly connected.

The AM-LCD having the construction as described above features a highdrivability, a high reliability and a high productivity on the groundthat the respective circuits are formed of the TFTs of appropriatestructures in accordance with their functions.

The present invention constructed as explained above will be describedin more detail in conjunction with examples below.

Embodiments

Embodiment 1

In this embodiment, there will be described a fabricating process forrealizing the structure of FIG. 4(C) detailed as one aspect ofperformance of the present invention before. Reference will be had toFIGS. 2(A)-2(D), FIGS. 3(A)-3(D) and FIGS. 4(A)-4(C).

First, a glass substrate 201 is prepared as a starting substrate. Asilicon oxide film (also called a “base film”) 202 being 200 [nm] thick,and an amorphous silicon film 203 a being 55 [nm] thick are formed onthe glass substrate 201 by sputtering them consecutively withoutexposing the substrate to the atmospheric air (FIG. 2(A)). Thus, boronand the like impurities contained in the atmospheric air can beprevented from adsorbing onto the lower surface of the amorphous siliconfilm 203 a.

By the way, although the amorphous silicon film was used as an amorphoussemiconductor film in an example of this embodiment, anothersemiconductor film may well be used. An amorphous silicon germanium filmmay well be employed. In addition, any of PCVD (plasma-assisted chemicalvapor deposition) LPCVD (low-pressure chemical vapor deposition),sputtering, etc. can be employed as an expedient for forming the basefilm and the semiconductor film. Among them, the sputtering is desirablebecause it is excellent in the points of safety and productivity. Asputtering apparatus used in this embodiment includes a chamber, anevacuation system for bringing the interior of the chamber into avacuum, a gas introduction system for introducing a sputtering gas intothe chamber, an electrode system configured of a target, an RF (radiofrequency) electrode, etc., and a sputtering power source connected tothe electrode system. In the example of this embodiment, argon (Ar) wasused as the sputtering gas, and a silicon target as the target.

Since, in this embodiment, the channel forming region of the TFT of apixel unit is to be made of the amorphous silicon film (the field effectmobility M_(FE) of the NTFT made from the amorphous silicon film islower than 1.0 [cm²/Vs]), the channel length of the TFT and thethickness of the amorphous silicon film need to be set at appropriatevalues.

Subsequently, the part 204 a of the amorphous silicon film 203 a iscrystallized. A known technique, such as laser crystallization orthermal crystallization employing a catalyst element, is used as anexpedient for the crystallization. In the example of this embodiment,the laser crystallization was implemented in conformity with the laserirradiation method schematically illustrated in FIG. 1. A laser beamemitted from an excimer-laser light source 105 had its beam shape,energy density, etc. regulated by an optical system (beam homogenizers106, a mirror 107, etc.), thereby to define a laser spot 108. Besides,an X-Y stage 104 to which the substrate 201 (101 in FIG. 1) was fixedwas moved in an X-direction or a Y-direction, whereby only the amorphoussemiconductor film of each driver circuit 103 was irradiated with thelaser spot 108 in a laser spot scanning direction 109. Thus, only theregion of the driver circuit was subjected to the laser irradiation andwas selectively crystallized, and the region 204 a made of a crystallinesilicon (polysilicon) film was formed (FIG. 2(B)).

Since, in this embodiment, the channel forming region of the TFT of thedriver circuit is to be made of the crystalline silicon film (the fieldeffect mobility M_(FE) of the NTFT made from the crystalline siliconfilm is 1.0 [cm²/Vs] or higher), the optimum channel length of the TFTand the thickness of the amorphous silicon film enough to belaser-crystallized need to be appropriately set. Considering thesenecessities, the channel length may be 3-10 [μm], and the thickness ofthe amorphous silicon film may be 10-200 [nm], preferably 30-70 [nm].

Thereafter, the crystalline silicon (polysilicon) film 204 a obtained ispatterned to form the semiconductor layer 204 b of the TFT of the drivercircuit, and the resulting amorphous silicon film 203 a is patterned toform the semiconductor layer 203 b of the TFT of the pixel unit (FIG.2(C)).

Incidentally, before or after forming the respective semiconductorlayers 203 b, 204 b of the TFTs of the pixel unit and the drivercircuit, the crystalline silicon film 204 a may well be doped with animpurity element (phosphorus or boron) for controlling the thresholdvoltage of the TFT of the driver circuit. This step may be implementedfor only the NTFT or PTFT, or for both the NTFT and PTFT.

Subsequently, a gate insulating film 205 is formed by sputtering orplasma CVD, whereupon a first conductive film 206 a and a secondconductive film 207 a are stacked and formed by sputtering (FIG. 2(D)).

The gate insulating film 205 is to function as the gate insulating filmsof the TFTs, and is endowed with a thickness of 50-200 [nm]. In theexample of this embodiment, a silicon oxide film being 100 [nm] thickwas formed by the sputtering which employed silicon oxide as a target.The mere silicon oxide film is not restrictive, but it can be replacedwith a stacked structure in which the silicon oxide film is overlaidwith a silicon nitride film. It is also allowed to employ a nitrifiedsilicon oxide film in which the silicon oxide film is doped withnitrogen.

By the way, this embodiment has mentioned the example in which, afterthe laser crystallization of the amorphous silicon film is carried out,the patterning is implemented, followed by the formation of the gateinsulating film. However, the fabricating process is not especiallyrestricted to the sequence of the steps, but it may well be replacedwith a process in which, after the amorphous silicon film and the gateinsulating film are consecutively formed by sputtering, the lasercrystallization is carried out, followed by the implementation of thepatterning. In the case of consecutively forming the films by thesputtering, good interface properties are attained.

In addition, the first conductive film 206 a is made of a conductivematerial whose main component is an element selected from the groupconsisting of Ta (tantalum), Ti (titanium), Mo (molybdenum) and W(tungsten). The thickness of the first conductive film 206 a may be setat 5-50 [nm], preferably 10-25 [nm]. On the other hand, the secondconductive film 207 a is made of a conductive material whose maincomponent is an element Al (aluminum), Cu (copper) or Si (silicon). Thethickness of the second conductive film 207 a may be set at 100-1000[nm], preferably 200-400 [nm]. The second conductive film 207 a isprovided in order to lower the wiring resistance of a gate wiring lineor a gate bus line.

At the next step, the unnecessary part of the second conductive film 207a is removed by patterning, whereby an electrode 207 b to become part ofthe gate bus line is formed in a wiring portion. Thereafter, resistmasks 208 a-208 d are formed. More specifically, the resist mask 208 ais formed so as to cover the PTFT of the driver circuit, while theresist mask 208 b is formed so as to cover the channel forming region ofthe NTFT of the driver circuit. Besides, the resist mask 208 c is formedso as to cover the electrode 207 b, while the resist masks 208 d areformed so as to cover the channel forming regions of the pixel unit.Further, using the resist masks 208 a-208 d, the resulting substrate isdoped with an impurity element bestowing the n-conductivity type,thereby to form impurity regions 210, 211 (FIG. 3(A)).

In the example of this embodiment, phosphorus (P) was used as theimpurity element bestowing the n-conductivity type, and ion doping wascarried out by employing phosphine (PH₃). Since, at this step, theelement phosphorus is passed through the gate insulating film 205 andthe first conductive film 206 a so as to dope the underlyingsemiconductor layers 203 b, 204 b with the element phosphorus, theacceleration voltage of the ion doping is set at a somewhat high voltageof 80 [keV]. The concentration of the element phosphorus to beintroduced into the semiconductor layers 203 b, 204 b as a dopant,should preferably be set within a range of 1×10¹⁶-1×10¹⁹ [atoms/cm³].Here in the example, the concentration was set at 1×10¹⁸ [atoms/cm³].Thus, the regions 210, 211 doped with the element phosphorus are formedin the semiconductor layers. Parts of the phosphorus-doped regionsformed here function as LDD regions. Besides, parts of regions coveredwith the masks and not doped with the element phosphorus (regions 209made of the crystalline silicon film, and regions 212 made of theamorphous silicon film) function as the channel forming regions.

Incidentally, the step of doping with the element phosphorus may beimplemented by either of ion implantation which separates masses andplasma doping which does not separate masses. Regarding such conditionsas the acceleration voltage and the dose, a person who controls thefabricating method may be set the optimum values.

Subsequently, the resist masks 208 a-208 d are removed, and anactivating process is carried out if necessary. Besides, a thirdconductive film 213 a is formed by sputtering (FIG. 3(B)). The thirdconductive film 213 a is made of the conductive material whose maincomponent is the element selected from the group consisting of Ta(tantalum), Ti (titanium), Mo (molybdenum) and W (tungsten). Besides,the thickness of the third conductive film 213 a is set at 100-1000[nm], preferably 200-500 [nm].

Subsequently, resist masks 214 a-214 d are formed anew, and theconductive film 213 a, etc. are patterned, thereby to form the gateelectrode 206 b, 213 b of the PTFT and to form the wiring line 206 c,213 c. Thereafter, using the masks 214 a-214 d left intact, theresulting substrate is doped with an impurity element bestowing thep-conductivity type, thereby to form the source region and drain regionof the PTFT (FIG. 3(C)). Here in the example, boron (B) was used as theimpurity element, and ion doping was carried out by employing diborane(B₂H₆). Also here, the acceleration voltage of the ion doping was set at80 [keV], and the element boron was introduced at a concentration of2×10²⁰ [atoms/cm³].

Subsequently, the resist masks 214 a-214 d are removed, and resist masks218 a-218 e are formed anew. Thereafter, using the resist masks 218a-218 e, the resulting substrate is etched so as to form the gate wiringline 206 d, 213 d of the NTFT of the driver circuit, the gate wiringlines 206 e, 213 e of the TFT of the pixel unit, and the upper wiringline 206 f, 213 f of a retention capacitance (FIG. 3(D)).

Next, the resist masks 218 a-218 e are removed, and resist masks 219 areformed anew. Thereafter, the resulting substrate is doped with animpurity element bestowing the n-conductivity type on the source regionsand drain regions of the NTFTs, thereby to form impurity regions 202-225(FIG. 4(A)). Here in the example, ion doping was carried out byemploying phosphine (PH₃). The concentration of phosphorus contained inthe impurity regions 220-225 is higher as compared with the phosphorusconcentration at the foregoing step of doping with the impurity elementwhich bestows the n-conductivity type, and it should preferably be setat 1×10¹⁹-1×10²¹ [atoms/cm³]. Here in the example, the concentration wasset at 1×10²⁰ [atoms/cm³].

Thereafter, the resist masks 219 are removed, and a protective film 227made of a silicon nitride film having a thickness of 50 [nm] is formed.Then, a state illustrated in FIG. 4(B) is obtained.

Subsequently, an activating process is carried out for activating theintroduced impurity element which bestows the nor p-conductivity type.The processing step may be implemented by thermal annealing whichemploys an electric heating furnace, laser annealing which employs theexcimer laser explained before, or rapid thermal annealing (RTA) whichemploys a halogen lamp. In the case of heat treatment, a heatingtemperature is set at 300-700 [° C.], preferably 350-550 [° C.]. In theexample of this embodiment, the resulting substrate was heat-treated at450 [° C.] in a nitrogen atmosphere for 2 hours.

Subsequently, a first interlayer insulating film 230 is formed, contactholes are provided, and source electrodes and drain electrodes 231-235,etc. are formed by known techniques.

Thereafter, a passivation film 236 is formed. Usable as the passivationfilm 236 is a silicon nitride film, an oxidized silicon nitride film, anitrified silicon oxide film, or a stacked film consisting of such aninsulating film and a silicon oxide film. In the example of thisembodiment, the silicon nitride film having a thickness of 300 [nm] wasused as the passivation film 236.

By the way, in this embodiment, a plasma process employing ammonia gasis carried out as preprocessing for the formation of the silicon nitridefilm, and it is directly followed by the formation of the passivationfilm 236. Since hydrogen activated (excited) by a plasma owing to thepreprocessing is confined within the passivation film 236, hydrogentermination in the active layers (semiconductor layers) of the TFTs canbe promoted.

Further, in a case where nitrous oxide gas is added into a gascontaining hydrogen, the surface of the object to-be-processed (theresulting substrate) is washed with a produced water content, and it canbe effectively prevented from being contaminated especially with boronetc. contained in the atmospheric air.

When the passivation film 236 has been formed, an acrylic resin filmbeing 1 [μm] thick is formed as a second interlayer insulating film 237.Thereafter, a contact hole is provided by patterning the films 236 and237, and a pixel electrode 238 made of an ITO film is formed. In thisway, the AM-LCD of the structure as shown in FIG. 4(C) is finished up.

Owing to the above steps, the NTFT of the driver circuit is formed withthe channel forming region 209, impurity regions 220, 221, and LDDregions 228. The impurity region 220 serves as a source region, whilethe impurity region 221 serves as a drain region. Besides, the NTFT ofthe pixel unit is formed with the channel forming regions 212, impurityregions 222-225, and LDD regions 229. Here, each of the LDD regions 228,229 is formed with a region overlapped by the gate electrode (GOLDregion: Gate-drain Overlapped LDD region), and a region not overlappedby the gate electrode (LDD region).

On the other hand, the P-conductivity type TFT of the driver circuit isformed with a channel forming region 217 and impurity regions 215, 216.Here, the impurity region 215 serves as a source region, while theimpurity region 216 serves as a drain region.

In this manner, the present invention features the point of forming onthe identical substrate the TFT of the pixel unit having the channelforming regions 212 made of the amorphous silicon film, and the TFTs ofthe driver circuit having the channel forming regions 209, 217 made ofthe crystalline silicon film. Owing to such a construction, it ispermitted to form the TFTs of the pixel unit having a high uniformityand the TFTs of the driver circuit having a high mobility on theidentical substrate.

FIG. 5(A) illustrates an example of the circuit arrangement of a liquidcrystal display device of active matrix type. The active matrix typeliquid crystal display device in this embodiment comprises a sourcesignal line side driver circuit 301, a gate signal line side drivercircuit (A) 307, a gate signal line side driver circuit (B) 311, aprecharge circuit 312, and a pixel unit 306.

The source signal line side driver circuit 301 includes a shift registercircuit 302, a level shifter circuit 303, a buffer circuit 304, and asampling circuit 305.

On the other hand, the gate signal line side driver circuit (A) 307includes a shift register circuit 308, a level shifter circuit 309, anda buffer circuit 310. The gate signal line side driver circuit (B) 311is similarly constructed.

In this embodiment, the circuits except the pixel unit are constructedas the driver circuits, and the semiconductor layers of thecorresponding regions are crystallized, but the present invention is notespecially restricted thereto. More specifically, those of the drivercircuits for which a reliability is required rather than a high mobilityneed not be crystallized. By way of example, the buffer circuit in eachof the driver circuits may well have the channel forming region of itsTFT made of a semiconductor layer of amorphous state likewise to that ofthe NTFT of the pixel unit.

Moreover, according to the present invention, the lengths of LDD regionsare readily made unequal on an identical substrate in consideration ofthe drive voltages of the NTFTs, and the optimum shapes can be formedfor the TFTs constituting the respective circuits, by an identical step.

FIG. 5(B) illustrates the top plan view of the pixel unit. Since theA-A′ sectional structure of a TFT portion and the B-B′ sectionalstructure of a wiring portion correspond to those same referencenumerals as in FIG. 4(C). In FIG. 5(B), numeral 401 designates asemiconductor layer, numeral 402 agate electrode, and symbol 403 a acapacitor line. In this embodiment, each of the gate electrode 402 and agate wiring line 403 b is formed of a first conductive layer and a thirdconductive layer, and a gate bus line has a clad structure formed of thefirst conductive layer, a second conductive layer and the thirdconductive layer.

In addition, FIG. 10(A) illustrates the top plan view of a CMOS circuitwhich is the constituent part of the driver circuit, and it correspondsto FIG. 4(C). In this example, the active layers of the NTFT and PTFTlie in direct contact, and one drain electrode is shared. However, thepresent invention is not especially restricted to the above structure,but it may well employ a structure as shown in FIG. 10(B) (where theactive layers are perfectly separated).

Embodiment 2

In this embodiment, an example in which an amorphous semiconductor filmis selectively crystallized using a laser different from the laser inEmbodiment 1 will be described below with reference to FIG. 6. Sincethis embodiment is the same as Embodiment 1 except the step of the lasercrystallization, it shall be explained with note taken only of differentpoints.

First, a silicon oxide film (subbing film) and an amorphous silicon filmare consecutively formed on a substrate in conformity with thefabricating process of Embodiment 1. In the example of this embodiment,the substrate was a quartz substrate. By the way, the thickness of theamorphous silicon film should preferably be set at 100 [nm] or more inrelation to the absorption coefficient of the argon laser.

At the next step of the laser crystallization, the selected parts of theamorphous silicon film are crystallized by employing the irradiationmethod illustrated in FIG. 6. A laser beam emitted from an argon-laserlight source 605 had its beam shape, energy density, etc. regulated byan optical system (a beam expander 606, a galvanometer 607, an f-θ(flyeye) lens 608, etc.), thereby to define a laser spot 609. Besides,the laser spot 609 was vibrated in directions parallel to a laser spotscanning direction 610 by vibrating the galvanometer 607, while at thesame time, a one-axis operation stage 604 to which the substrate 601 wasfixed was moved step by step (the interval of the steps being nearlyequal to the diameter of the laser spot 609) in one direction (theoperating direction 611 of the one-axis operation stage 604). Thus, onlythe amorphous semiconductor film of each driver circuit 603 wasselectively crystallized, so that each region made of a crystallinesilicon (polysilicon) film was formed.

When the succeeding steps are conformed to those of Embodiment 1, thestate shown in FIG. 4(C) can be obtained.

Embodiment 3

In the fabricating process described in Embodiment 1 or 2, only thedriver circuits are selectively irradiated with the laser beam byemploying the laser irradiation method illustrated in FIG. 1 or FIG. 6.It is also possible, however, to irradiate the selected parts with thelaser beam by forming an ordinary resist mask.

In this case, a conventional laser irradiation apparatus is usable as itis. Accordingly, the laser irradiation can be easily implemented withoutaltering the apparatus, and it can be said an effective technique.

Moreover, the construction of this embodiment can be combined witheither of Embodiments 1 and 2 at will.

Embodiment 4

In this embodiment, an example in the case of fabricating an AM-LCD by aprocess different from that of Embodiment 1 will be described withreference to FIGS. 7(A)-7(C), FIGS. 8(A)-8(D) and FIGS. 9(A)-9(C).Whereas the top gate type TFTs have been exemplified in Embodiment 1,bottom gate type TFTs will be exemplified in this embodiment.

First, gate electrodes 702 of stacked structure (not shown for the sakeof brevity) are formed on a glass substrate 701. In the example of thisembodiment, a tantalum nitride film and a tantalum film were stacked andformed by sputtering, and they were worked into gate wiring lines(including the gate electrodes) 702 a-702 c and a capacitor wiring line702 d by known patterning.

Subsequently, a gate insulating film and an amorphous semiconductor filmare stacked and formed successively without exposing the substrate tothe atmospheric air. In the example of this embodiment, a stacked layerconsisting of a silicon nitride film 703 and a silicon oxide film 704was formed by the sputtering, and it was employed as the gate insulatingfilm of stacked structure. Next, an amorphous silicon film 765 as theamorphous semiconductor film was formed by the sputtering withoutexposing the substrate to the atmospheric air (FIG. 7(A)). Although theamorphous semiconductor film formed by the sputtering has a low hydrogenconcentration, a heat treatment for lessening, the hydrogenconcentration still further may well be carried out.

Since, in this embodiment, the channel forming region of the TFT of apixel unit is to be made of the amorphous silicon film (the field effectmobility M_(FE) of the NTFT made from the amorphous silicon film islower than 1.0 [cm²/Vs]), the channel length of the TFT and thethickness of the amorphous silicon film need to be set at appropriatevalues.

Subsequently, the amorphous silicon film 705 is selectively subjected tolaser crystallization, thereby to form a crystalline silicon film 706.In the example of this embodiment, only each of driver circuits wasirradiated with a laser beam by employing the laser irradiation methodillustrated in FIG. 1 (FIG. 7(B)).

Since, in this embodiment, the channel forming region of the TFT of thedriver circuit is to be made of the crystalline silicon film (the fieldeffect mobility M_(FE) of the NTFT made from the crystalline siliconfilm is 1.0 [cm²/Vs] or higher), the optimum channel length of the TFTand the thickness of the amorphous silicon film enough to belaser-crystallized need to be appropriately set. Considering thesenecessities, the channel length may be 3-10 [Mm], and the thickness ofthe amorphous silicon film may be 10-200 [nm], preferably 30-70 [nm].

Subsequently, a channel protection film 707 for protecting the channelforming regions is formed. The channel protection film 707 may be formedby known patterning. In the example of this embodiment, the film 707 waspatterned using a photo-mask. In this state, the upper surface of thecrystalline silicon film or amorphous silicon film except regions lyingin touch with the channel protection film 707 is denuded (FIG. 7(C)). Bythe way, in a case where the film 707 is patterned by exposing the rearsurface of the resulting substrate to light, the photo-mask isunnecessary, and hence, the number of processing steps can be decreased.

Subsequently, a resist mask 708 which covers parts of the PTFT and NTFTof the driver circuit and the NTFT of the pixel unit is formed bypatterning which employs a photo-mask. Next, the resulting substrate isdoped with an impurity element bestowing the n-conductivity type(phosphorus in this embodiment), thereby to form impurity regions 709(FIG. 8(A)).

Subsequently, the resist mask 708 is removed, and the whole surface ofthe resulting substrate is covered with a thin insulating film 710. Thethin insulating film 710 is formed in order to dope the substrate withan impurity element at a lower concentration later, and it is not alwaysnecessary (FIG. 8(B)).

Subsequently, the resulting substrate is doped with the impurity elementat the concentration which is lower as compared with the phosphorusconcentration at the preceding step of doping with the impurity element(FIG. 8(C)). Owing to the step shown in FIG. 8(C), the part of thecrystalline silicon film covered with the channel protection film 707(707 b in FIG. 7(C)) is turned into the channel forming region 713, andthe parts of the amorphous silicon film covered with the channelprotection film 707 (707 c in FIG. 7(C)) are turned into the channelforming regions 714. In addition, the LDD regions 711, 712 of the NTFTsare formed by this step.

At the next step, a resist mask 715 which covers the entire surfaces ofthe N-channel TFTs is formed, and the resulting substrate is doped withan impurity element which bestows the p-conductivity type (FIG. 8(D)).Owing to this step, the part of the crystalline silicon film coveredwith the channel protection film 707 (707 a in FIG. 7(C)) is turned intothe channel forming region 716 of the PTFT, and the source region anddrain region 717 of the PTFT are formed.

Subsequently, the resist mask 715 is removed, and the semiconductorlayers are patterned into desired shapes (FIG. 9(A)).

Subsequently, a first interlayer insulating film 722 is formed, contactholes are provided, and source electrodes and drain electrodes 723-727,etc. are formed by known techniques.

Thereafter, a passivation film 728 is formed (FIG. 9(B)). Usable as thepassivation film 728 is a silicon nitride film, an oxidized siliconnitride film, a nitrified silicon oxide film, or a stacked filmconsisting of such an insulating film and a silicon oxide film. In theexample of this embodiment, the silicon nitride film having a thicknessof 300 [nm] was used as the passivation film 728.

By the way, in this embodiment, a plasma process employing ammonia gasis carried out as preprocessing for the formation of the silicon nitridefilm, and it is directly followed by the formation of the passivationfilm 728. Since hydrogen activated (excited) by a plasma owing to thepreprocessing is confined within the passivation film 728, hydrogentermination in the active layers (semiconductor layers) of the TFTs canbe promoted.

When the passivation film 728 has been formed, an acrylic resin filmbeing 1 [μm] thick is formed as a second interlayer insulating film 729.Thereafter, a contact hole is provided by patterning the films 728 and729, and a pixel electrode 730 made of an ITO film is formed. In thisway, the AM-LCD of the structure as shown in FIG. 9(C) is finished up.

Moreover, the construction of this embodiment can be combined witheither of Embodiments 2 and 3 at will.

Embodiment 5

In this embodiment, there will be described a case where anotherexpedient is employed for the formation of a crystalline silicon film inEmbodiment 1.

Concretely, a technique disclosed as Embodiment 2 in the officialgazette of Japanese Patent Application Laid-open No. 130652/1995(corresponding to U.S. Pat. No. 08/329,644) is adopted for thecrystallization of an amorphous silicon film. The technique disclosed inthe official gazette is such that a catalyst element promotingcrystallization (cobalt, vanadium, germanium, platinum, iron or copper,and typically nickel) is borne on the selected part of the surface ofthe amorphous silicon film, and that the amorphous silicon film iscrystallized using the part as the seed of nucleus growth.

According to the technique, crystal growth can be endowed with aspecified orientation, and hence, the crystalline silicon film of veryhigh crystallinity can be formed.

Incidentally, the construction of this embodiment can be combined withthe construction of any of Embodiments 1-4 at will.

Embodiment 6

In this embodiment, there will be described a case where anotherexpedient is employed for the formation of a crystalline silicon film inEmbodiment 1.

In an example of this embodiment, nickel is selected as a catalystelement, a nickel containing layer is formed on an amorphous siliconfilm, and the amorphous silicon film is selectively irradiated with alaser beam, thereby to be crystallized.

Subsequently, a resist mask is formed on the resulting silicon film, soas to implement the step of doping the resulting substrate with anelement which belongs to the 15th family of elements (phosphorus in thisembodiment). The concentration of the element phosphorus to beintroduced as a dopant should preferably be 5×10¹⁸-1×10²⁰ [atoms/cm³],(more preferably, 1×10¹⁹-5×10¹⁹ [atoms/cm³]. Since, however, theconcentration of the dopant phosphorus to be introduced changesdepending upon the temperature and time period of a later gettering stepand the area of phosphorus-doped regions, the above concentration rangeis not restrictive. Thus, the regions doped with the element phosphorus(the phosphorus-doped regions) are formed.

The resist mask is arranged so as to denude part (or the whole) of aregion which is to become the source region or drain region of the TFTof each driver circuit later. Likewise, the resist mask is arranged soas to denude part (or the whole) of a region which is to become thesource region or drain region of the TFT of a pixel unit later. On thisoccasion, the resist mask is not arranged on a region which is to becomethe lower electrode of a retention capacitor, and hence, the region isentirely doped with the dopant phosphorus into the phosphorus-dopedregion.

Subsequently, the resist mask is removed, and a heat treatment at500-650[° C.] is carried out for 2-16 [hours], thereby to getter thecatalyst element (nickel in this embodiment) used for thecrystallization of the silicon film. A temperature on the order of ±50[° C.] with respect to the highest temperature of a thermal hysteresisis required for attaining a gettering action. In this regard, a heattreatment for the crystallization is implemented at 550-600 [° C.], sothat the heat treatment at 500-650 [° C.] suffices to attain thegettering action.

Besides, the crystalline silicon (polysilicon) film from which thecatalyst element has been diminished is patterned, thereby to form thecrystalline semiconductor layer of the TFT of the driver circuit and theamorphous semiconductor layer of the TFT of the pixel unit. Thesucceeding steps may be conformed to those of Embodiment 1.

Incidentally, the construction of this embodiment can be combined withthe construction of any of Embodiments 1-5 at will.

Embodiment 7

In this embodiment, there will be described an example in which sourceregions and drain regions of TFTs are formed by doping semiconductorlayers with elements which belong to the 13th family and 15th family ofelements, in a sequence different from the doping sequence inEmbodiment 1. In the present invention, the sequence of dopingoperations can be altered on occasion. The doping sequence exemplifiedin Embodiment 1 is such that the dopant phosphorus at the lowconcentration is first introduced, that the dopant boron is secondlyintroduced, and that the dopant phosphorus at the high concentration isthirdly introduced. In the example of this embodiment, the dopantphosphorus at the high concentration is first introduced after the stateshown in FIG. 3(B) has been obtained.

The state of FIG. 3(B) is obtained in conformity with the processingsteps of Embodiment 1.

Subsequently, a resist mask for forming the wiring lines of the NTFTs isformed. The resist mask covers the region of the PTFT of the drivercircuit. Using the resist mask, the resulting substrate is etched so asto form the gate wiring line of the NTFT of the driver circuit, the gatewiring lines of the TFT of the pixel unit, and the upper wiring line ofthe retention capacitance.

Subsequently, the resist mask is removed, and a resist mask is formed anew. Thereafter, the resulting substrate is doped with the impurityelement bestowing the n-conductivity type on the source regions anddrain regions of the NTFTs, thereby to form impurity regions. On thisoccasion, the concentration of the element phosphorus to be introducedis 5×10¹⁹-1×10²¹ [atoms/cm³].

Next, a resist mask which covers a region except the region of the PTFTis formed. In this state, the step of doping with the element boron isimplemented. On this occasion, the concentration of the element boron tobe introduced is 1×10²⁰-3×10²¹ [atoms/cm³]. Thus, the source region,drain region and channel forming region of the PTFT are defined.

The succeeding steps may be conformed to the fabricating process ofEmbodiment 1. The construction of this embodiment can be combined withthe construction of any of Embodiments 1-6 at will.

Embodiment 8

The present invention is also applicable to a case where an interlayerinsulating film is formed on conventional MOSFETs(metal-oxide-semiconductor field effect transistors), and where TFTs areformed on the interlayer insulating film. That is, the present inventioncan incarnate a semiconductor device of multilevel structure in which areflection type AM-LCD is formed on a semiconductor circuit.

Besides, the above semiconductor circuit may well be one formed on anSOI (Silicon On Insulator) substrate such as “SIMOX” or “Smart-Cut”(registered trademark of SOITEC Inc.) or “ELTRAN” (registered trademarkof Canon Inc.).

By the way, in performing this embodiment, the construction of any ofEmbodiments 1-7 may well be combined.

Embodiment 9

In this embodiment, there will be described a case where TFTs wereformed on a substrate by the fabricating process of Embodiment 1, andwhere an AM-LCD was actually fabricated.

When the state of FIG. 4(C) has been obtained, an orientation film isformed on the pixel electrode 238 to a thickness of 80 [nm].Subsequently, a glass substrate on which a color filter, a transparentelectrode (counter electrode) and an orientation film are formed isprepared as a counter substrate, and the respective orientation filmsare subjected to rubbing. The substrate formed with the TFTs, and thecounter substrate are stuck together by the use of a sealing member.Besides, a liquid crystal is held between both the substrates. Such acell assemblage step may be resorted to a known expedient, and shall beomitted from detailed description.

Incidentally, a spacer for keeping a cell gap may be disposed ifnecessary. It need not be especially disposed in a case where the cellgap can be kept without any spacer as in an AM-LCD which is at most 1[inch] long diagonally.

The external appearance of the AM-LCD fabricated in the above way, isillustrated in FIG. 11. As shown in FIG. 11, an active matrix substrateand the counter substrate oppose to each other, and the liquid crystalis sandwiched in between the substrates. The active matrix substrateincludes a pixel unit 1001, a scanning line driver circuit 1002 and asignal line driver circuit 1003 which are formed on the substrate 1000.

The scanning line driver circuit 1002 and the signal line driver circuit1003 are respectively connected to the pixel unit 1001 by scanning lines1030 and signal lines 1040. Each of the driver circuits 1002, 1003 ismainly constructed of a CMOS circuit.

The scanning line 1030 is laid every row of the pixel unit 1001, whilethe signal line 1040 is laid every column thereof. The TFT 1010 of thepixel unit is formed in the vicinity of the intersection part betweenthe scanning line 1030 and the signal line 1040. The gate electrodes ofthe TFT 1010 of the pixel unit are connected to the scanning line 1030,and the source thereof is connected to the signal line 1040. Further, apixel electrode 1060 and a retention capacitance 1070 are connected tothe drain of the TFT 1010.

The counter substrate 1080 is formed with a transparent conductive film,such as ITO film, over its whole surface. The transparent conductivefilm functions as a counter electrode for the pixel electrode 1060 ofthe pixel unit 1001, and the liquid crystal material is driven by anelectric field established between the pixel electrode and the counterelectrode. If necessary, the counter substrate 1080 is formed with theorientation film, a black mask or a color filter.

IC chips 1032, 1033 are mounted on the substrate of the active matrixsubstrate side by utilizing a surface to which an FPC (flexible printedcircuit) 1031 is attached. The IC chips 1032, 1033 are so constructedthat circuits, such as a video signal processing circuit, a timing pulsegenerator circuit, a γ correction circuit, a memory circuit and anarithmetic circuit, are formed on a silicon substrate.

Further, although the liquid crystal display device is exemplified inthis embodiment, the present invention is also applicable to any displaydevice of active matrix type, such as an EL (electroluminescent) displaydevice or an EC (electrochromic) display device.

Incidentally, this embodiment can be combined with any of Embodiments1-8 at will.

Embodiment 10

In this embodiment, an example in which an EL display device of activematrix type was fabricated by adopting the present invention will bedescribed with reference to FIG. 12 and FIGS. 13(A) and 13(B).

FIG. 12 schematically shows the circuit diagram of the active matrixtype EL display device. Numeral 11 designates a pixel unit, around whichan X-directional driver circuit 12 and a Y-directional driver circuit 13are disposed. In addition, each pixel of the pixel unit 11 includes aswitching TFT 14, a capacitor 15, a current controlling TFT 16 and anorganic EL element 17. Herein, an X-directional signal line 18 a (or 18b) and a Y-directional signal line 20 a (20 b or 20 c) are connected tothe switching TFT 14. Also, a power source line 19 a (or 19 b) isconnected to the current controlling TFT 16.

In this embodiment, the semiconductor layers of TFTs in theX-directional driver circuit 12 as well as the Y-directional drivercircuit 13 are made of polysilicon, whereas the semiconductor layers ofthe TFTs in the pixel unit 11 are made of amorphous silicon.

Besides, the TFTs in the X-directional driver circuit 12 as well as theY-directional driver circuit 13 have the GOLD structure, whereas theswitching TFT 14 and the current controlling TFT 16 have the LDDstructure.

FIG. 13(A) is the top plan view of the EL display device adopting thepresent invention. Referring to the figure, numeral 4010 designates asubstrate, numeral 4011 a pixel unit, numeral 4012 a source side drivercircuit, and numeral 4013 a gate side driver circuit. The respectivedriver circuits are led to an FPC 4017 (FIG. 13(B)) via wiring lines4014-4016, and are connected to an external equipment.

On this occasion, a cover member 6000, a sealing member (also termed“housing member”) 7000 (FIG. 13(B)), and a hermetic seal member (secondsealing member) 7001 are disposed so as to surround, at least, the pixelunit, and preferably, the driver circuits and the pixel unit.

In addition, FIG. 13(B) illustrates the sectional structure of the ELdisplay panel of this embodiment. TFTs for the driver circuit, 4022(here, a CMOS circuit in which an n-channel TFT and a p-channel TFT arecombined is depicted), and a TFT for the pixel unit, 4023 (here, onlythe TFT for controlling current toward the EL element is depicted) areformed on a substrate 4010 as well as a base film 4021. Here in theillustrated example, the TFTs are the bottom gate type TFTs based on thefabricating method of Embodiment 4. However, this is not especiallyrestrictive, but the TFTs may have a known structure (top-gate structureor bottom-gate structure).

When the driver circuit TFTs 4022 having active layers made ofcrystalline semiconductor films and the pixel unit TFT 4023 having anactive layer made of an amorphous semiconductor film have been finishedup by adopting the present invention, a pixel electrode 4027 which ismade of a transparent conductive film and which is electricallyconnected with the drain of the pixel unit TFT 4023 is formed on aninterlayer insulating film (a flattening film) 4026 which is made of aresin material. A compound (called “ITO”) of indium oxide and tin oxide,or a compound of indium oxide and zinc oxide can be used for thetransparent conductive film. Besides, after the formation of the pixelelectrode 4027 serving as an anode, an insulating film 4028 is depositedand is formed with an opening on the pixel electrode 4027.

Subsequently, an EL layer 4029 is formed. The EL layer 4029 may beconstructed into a multilayer structure or a single-layer structure byoptionally combining known EL materials (a hole injection layer, a holetransport layer, a luminescent layer, an electron transport layer, andan electron injection layer). The structure may be determined by knowntechniques. Besides, the EL materials are classified into low-molecularmaterials and high-molecular (polymer) materials. In case of employingthe low-molecular material, vapor deposition is relied on, whereas incase of employing the high-molecular material, a simple method such asspin coating, ordinary printing or ink jet printing can be relied on.

In this embodiment, the EL layer is formed in accordance with vapordeposition by employing a shadow mask. Luminescent layers (redluminescent layer, green luminescent layer and blue luminescent layer)capable of luminescences of different wavelengths are formed every pixelby employing the shadow mask, whereby a color display becomes possible.There are also a scheme in which color conversion measures (CCM) andcolor filters are combined, and a scheme in which a white luminescentlayer and color filters are combined, and any of such methods may wellbe employed. Of course, an EL display panel of monochromaticluminescence can be constructed.

After the EL layer 4029 has been formed, it is overlaid with a cathode4030. Moisture and oxygen to exist at the boundary between the cathode4030 and the EL layer 4029 should desirably be excluded to the utmostbeforehand. Accordingly, such a contrivance is required that the ELlayer 4029 and the cathode 4030 are consecutively formed in vacuum, orthat the EL layer 4029 is formed in an inactive atmosphere, followed byforming the cathode 4030 without exposing the resulting substrate to theatmospheric air. In this embodiment, the film formation as explainedabove is incarnated by employing a film forming equipment ofmultichamber system (cluster tool system).

By the way, in this embodiment, the multilayer structure consisting ofan LiF (lithium fluoride) film and an Al (aluminum) film is employed forthe cathode 4030. More concretely, the LiF film being 1 [nm] thick isformed on the EL layer 4029 by vapor deposition, and it is overlaid withthe Al film being 300 [nm] thick. It is, of course, allowed to employ anMgAg electrode which is a known cathode member. Besides, the cathode4030 is connected to the wiring line 4016 in a region which is indicatedby numeral 4031. The wiring line 4016 is a supply voltage feed line forapplying a predetermined voltage to the cathode 4030, and it isconnected to the FPC 4017 through a conductive paste material 4032.

For the purpose of electrically connecting the cathode 4030 and thewiring line 4016 in the region 4031, contact holes need to be formed inthe interlayer insulating film 4026 and the insulating film 4028. Theymay be previously formed at the etching of the interlayer insulatingfilm 4026 (at the formation of the contact hole for the pixel electrode)and at the etching of the insulating film 4028 (at the formation of anopening before the formation of the EL layer). Alternatively, in etchingthe insulating film 4028, also the interlayer insulating film 4026 maybe etched in collective fashion. In this case, if the interlayerinsulating film 4026 and the insulating film 4028 are made of the sameresin material, the contact holes can be formed into favorable shapes.

A passivation film 6003, a filler member 6004 and the cover member 6000are formed covering the surface of the EL element thus formed.

Further, the sealing member 7000 is disposed between the cover member6000 and the substrate 4010 so as to surround the EL element portion,and the hermetic seal member (second sealing member) 7001 is formedoutside the sealing member 7000.

On this occasion, the filler member 6004 functions also as an adhesivefor bonding the cover member 6000. Usable for the filler member 6004 isPVC (polyvinyl chloride), an epoxy resin, a silicone resin, PVB(polyvinyl butylal) or EVA (ethylene vinyl acetate). When a drying agentis introduced into the filler member 6004 beforehand, favorably ahygroscopic effect can be kept.

Besides, a spacer may well be contained in the filler member 6004. Onthis occasion, a granular material made of BaO or the like may well beselected as the spacer, thereby to endow the spacer itself with ahygroscopicity.

In the case of disposing the spacer, the passivation film 6003 can relaxa spacer pressure. It is also allowed to dispose a resin film or thelike relaxing the spacer pressure, separately from the passivation film6003.

Usable as the cover member 6000 is a glass plate, an aluminum plate, astainless steel plate, an FRP (Fiberglass-Reinforced Plastics) plate, aPVF (polyvinyl fluoride) film, a Mylar film, a polyester film, or anacrylic film. By the way, in the case of using the substance PVB or EVAfor the filler member 6004, it is favorable to employ a sheet having astructure in which an aluminum foil being several tens [μm] thick issandwiched in between the PVF films or the Mylar films.

Depending upon the direction of luminescence (the radiating direction oflight) from the EL element, however, the cover member 6000 needs to havea light transmitting property.

In addition, the wiring line 4016 is electrically connected to the FPC4017 by passing through the gap between the sealing member 7000 as wellas the hermetic seal member 7001 and the substrate 4010. Although thewiring line 4016 has been explained here, the other wiring lines 4014,4015 are electrically connected to the FPC 4017 by passing under thesealing member 7000 and the hermetic seal member 7001, likewise to thewiring line 4016.

Besides, in this embodiment, the pixel electrode is formed as the anode,and hence, a PTFT should preferably be employed as the currentcontrolling TFT. Regarding the fabricating process, Embodiment 4 may bereferred to. In the case of this embodiment, the light generated in theluminescent layer is radiated toward the substrate formed with the TFTs.Alternatively, the current controlling TFT may well be formed of theNTFT according to the present invention. In the case of employing theNTFT as the current controlling TFT, the pixel electrode (the cathode ofthe EL element) made of a conductive film of high reflectivity may beconnected with the drain of the pixel unit TFT 4023, whereupon an ELlayer and an anode made of a light-transmitting conductive film may beformed in succession. In this case, the light generated in theluminescent layer is radiated toward the substrate not formed with theTFTs.

Incidentally, this embodiment can be combined with any of Embodiments1-8 at will.

Embodiment 11

A CMOS circuit or a pixel unit which has been formed by performing thepresent invention, is applicable to various electrooptic devices (suchas an active matrix type liquid crystal display device, an active matrixtype EL display device, and an active matrix type EC display device).Accordingly, the present invention can be performed in all electronicequipment in which the electrooptic devices are incorporated as displayunits.

Mentioned as such electronic equipment are a video camera, a digitalcamera, a projector (of rear type or front type), a head-mounted typedisplay (goggle type display), a car navigation equipment, a personalcomputer, a portable information terminal (such as mobile computer,portable telephone set or electronic book), and so forth. Examples ofthem are illustrated in FIGS. 14(A)-14(F) and FIGS. 15(A)-15(C).

FIG. 14(A) shows a personal computer, which includes the body 2001, animage input unit 2002, a display unit 2003, and a keyboard 2004. Thepresent invention can be applied to the image input unit 2002, thedisplay unit 2003 and other signal controlling circuits.

FIG. 14(B) shows a video camera, which includes the body 2101, a displayunit 2102, a sound input unit 2103, operating switches 2104, a battery2105, and an image receiving unit 2106. The present invention can beapplied to the display unit 2102 and other signal controlling circuits.

FIG. 14(C) shows a mobile computer, which includes the body 2201, acamera unit 2202, an image receiving unit 2203, an operating switch2204, and a display unit 2205. The present invention can be applied tothe display unit 2205 and other signal controlling circuits.

FIG. 14(D) shows a part (the right side) of a head-mounted type ELdisplay, which includes the body 2301, signal cables 2302, a head-fixedband 2303, a display screen 2304, an optical system 2305, and a displaydevice 2306. The present invention can be adopted for the display device2306.

FIG. 14(E) shows a player which is used for a recording medium (2404)storing programs therein, and which includes the body 2401, a displayunit 2402, a loudspeaker unit 2403, and operating switches 2405. By theway, the recording medium 2404 is a DVD (Digital Versatile Disc), a CD(Compact Disc), or the like, and the player is capable of reproducingmusic, a motion picture, a video game or information obtained throughthe Internet. The present invention can be applied to the display unit2402 and other signal controlling circuits.

FIG. 14(F) shows a digital camera, which includes the body 2501, adisplay unit 2502, a view window 2503, operating switches 2504, and animage receiving portion (not shown). The present invention can beapplied to the display unit 2502 and other signal controlling circuits.

FIG. 15(A) shows a portable telephone set, which includes the body 2901,a voice output unit 2902, a voice input unit 2903, a display unit 2904,operating switches 2905, and an antenna 2906. The present invention canbe applied to the voice output unit 2902, the voice input unit 2903, thedisplay unit 2904, and other signal controlling circuits.

FIG. 15(B) shows a portable book (electronic book), which includes thebody 3001, display units 3002, 3003, a storage medium 3004, operatingswitches 3005, and an antenna 3006. The present invention can be appliedto the display units 3002, 3003, and other signal circuits.

FIG. 15(C) shows a display, which includes the body 3101, a supporter3102, and a display panel 3103. The present invention can be applied tothe display panel 3103. The display according to the present inventionis meritorious especially in case of an enlarged panel which is at least10 [inches] (particularly, at least 30 [inches]) long diagonally.

As described above, the present invention has very wide applications andis applicable to electronic equipment in all fields. Moreover, theelectronic equipment of this embodiment can be realized with aconstruction which is in any combination of Embodiments 1-10.

Owing to the present invention, the respective circuits of anelectrooptic device represented by an AM-LCD or an EL display device canbe formed of TFTs of appropriate structures in accordance with thefunctions of the circuits, whereby the electrooptic device having a highreliability can be incarnated.

1. A method for forming a semiconductor device comprising: forming asemiconductor film over a substrate, said semiconductor film extendingin a pixel region and a driver circuit region; and irradiating acontinuous wave laser light to a part of said semiconductor film in atleast said driver circuit region to crystallize said part of saidsemiconductor film in at least said driver circuit region.
 2. A methodaccording to claim 1 wherein an active layer of an N-channel thin filmtransistor of said driver circuit region is formed in the crystallizedpart of said semiconductor film.
 3. A method according to claim 1wherein an active layer of a P-channel thin film transistor of saiddriver circuit region is formed in the crystallized part of saidsemiconductor film.
 4. A method according to claim 2 wherein said activelayer comprises a source region, a drain region, a channel region and alightly doped drain region.
 5. A method according to claim 3 whereinsaid active layer comprises a source region, a drain region, a channelregion and a lightly doped drain region.
 6. A method according to claim1 wherein a shift register circuit is formed in said driver circuitregion.
 7. A method according to claim 1 wherein a level shifter circuitis formed in said driver circuit region.
 8. A method according to claim1 wherein a buffer circuit is formed in said driver circuit region.
 9. Amethod according to claim 1 wherein a sampling circuit is formed in saiddriver circuit region.
 10. A method according to claim 1 wherein saidcontinuous wave laser light is an argon laser light.
 11. A methodaccording to claim 1 wherein said semiconductor device is incorporatedinto one selected from the group consisting of personal computer, videocamera, mobile computer, head-mount display, player used for recordingmedium storing programs, digital camera, portable telephone, portablebook, and display.
 12. A method for forming a semiconductor devicecomprising: forming a semiconductor film over a substrate, saidsemiconductor film extending in a pixel region and a driver circuitregion; and irradiating a continuous wave laser light to a part of saidsemiconductor film in at least said driver circuit region while movingsaid substrate relative to said continuous wave laser light tocrystallize said part of said semiconductor film in at least said drivercircuit region.
 13. A method according to claim 12 wherein an activelayer of an N-channel thin film transistor of said driver circuit regionis formed in the crystallized part of said semiconductor film.
 14. Amethod according to claim 12 wherein an active layer of a P-channel thinfilm transistor of said driver circuit region is formed in thecrystallized part of said semiconductor film.
 15. A method according toclaim 13 wherein said active layer comprises a source region, a drainregion, a channel region and a lightly doped drain region.
 16. A methodaccording to claim 14 wherein said active layer comprises a sourceregion, a drain region, a channel region and a lightly doped drainregion.
 17. A method according to claim 12 wherein a shift registercircuit is formed in said driver circuit region.
 18. A method accordingto claim 12 wherein a level shifter circuit is formed in said drivercircuit region.
 19. A method according to claim 12 wherein a buffercircuit is formed in said driver circuit region.
 20. A method accordingto claim 12 wherein a sampling circuit is formed in said driver circuitregion.
 21. A method according to claim 12 wherein said continuous wavelaser light is an argon laser light.
 22. A method according to claim 12wherein said semiconductor device is incorporated into one selected fromthe group consisting of personal computer, video camera, mobilecomputer, head-mount display, player used for recording medium storingprograms, digital camera, portable telephone, portable book, anddisplay.
 23. A method for forming an electroluminescent display devicecomprising: forming a semiconductor film over a substrate, saidsemiconductor film extending in a pixel region and a driver circuitregion; and irradiating a continuous wave laser light to a part of saidsemiconductor film in at least said driver circuit region to crystallizesaid part of said semiconductor film in at least said driver circuitregion.
 24. A method according to claim 23 wherein an active layer of anN-channel thin film transistor of said driver circuit region is formedin the crystallized part of said semiconductor film.
 25. A methodaccording to claim 23 wherein an active layer of a P-channel thin filmtransistor of said driver circuit region is formed in the crystallizedpart of said semiconductor film.
 26. A method according to claim 24wherein said active layer comprises a source region, a drain region, achannel region and a lightly doped drain region.
 27. A method accordingto claim 25 wherein said active layer comprises a source region, a drainregion, a channel region and a lightly doped drain region.
 28. A methodaccording to claim 23 wherein a shift register circuit is formed in saiddriver circuit region.
 29. A method according to claim 23 wherein alevel shifter circuit is formed in said driver circuit region.
 30. Amethod according to claim 23 wherein a buffer circuit is formed in saiddriver circuit region.
 31. A method according to claim 23 wherein asampling circuit is formed in said driver circuit region.
 32. A methodaccording to claim 23 wherein said continuous wave laser light is anargon laser light.
 33. A method according to claim 23 wherein saidelectroluminescent display device is incorporated into one selected fromthe group consisting of personal computer, video camera, mobilecomputer, head-mount display, player used for recording medium storingprograms, digital camera, portable telephone, and portable book.
 34. Amethod for forming a semiconductor device comprising: forming asemiconductor film over a substrate, said semiconductor film extendingin a pixel region and a driver circuit region; and irradiating acontinuous wave laser light to a part said semiconductor film in atleast said driver circuit region while moving said substrate relative tosaid continuous wave laser light to crystallize said part of saidsemiconductor film in at least said driver circuit region by using agalvanometer.
 35. A method according to claim 34 wherein an active layerof an N-channel thin film transistor of said driver circuit region isformed in the crystallized part of said semiconductor film.
 36. A methodaccording to claim 34 wherein an active layer of a P-channel thin filmtransistor of said driver circuit region is formed in the crystallizedpar of said semiconductor film.
 37. A method according to claim 35wherein said active layer comprises a source region, a drain region, achannel region and a lightly doped drain region.
 38. A method accordingto claim 36 wherein said active layer comprises a source region, a drainregion, a channel region and a lightly doped drain region.
 39. A methodaccording to claim 34 wherein a shift register circuit is formed in saiddriver circuit region.
 40. A method according to claim 34 wherein alevel shifter circuit is formed in said driver circuit region.
 41. Amethod according to claim 34 wherein a buffer circuit is formed in saiddriver circuit region.
 42. A method according to claim 34 wherein acircuit is formed in said driver circuit region.
 43. A method accordingto claim 34 wherein said continuous wave laser light is an argon laserlight.
 44. A method for forming a semiconductor device comprising;forming a semiconductor film over a substrate, said semiconductor filmextending in a pixel region and a driver circuit region; and irradiatinga continuous wave laser light to a part of said semiconductor film in atleast said driver circuit region to crystallize said part of saidsemiconductor film in at least said driver circuit region while a partof the semiconductor film in said pixel region is not irradiated withsaid continuous laser light.
 45. A method according to claim 44 whereinan active layer of an N-channel thin film transistor of said drivercircuit region is formed in the crystallized part of said semiconductorfilm.
 46. A method according to claim 44 wherein an active layer of aP-channel thin film transistor of said driver circuit region is formedin the crystallized part of said semiconductor film.
 47. A methodaccording to claim 45 wherein said active layer comprises a sourceregion, a drain region, a channel region and a lightly doped drainregion.
 48. A method according to claim 46 wherein said active layercomprises a source region, a drain region, a channel region and alightly doped drain region.
 49. A method according to claim 44 wherein ashift register circuit is formed in said driver circuit region.
 50. Amethod according to claim 44 wherein a level shifter circuit is formedin said driver circuit region.
 51. A method according to claim 44wherein a buffer circuit is formed in said driver circuit region.
 52. Amethod according to claim 44 wherein a sampling circuit is formed insaid driver circuit region.
 53. A method according to claim 44 whereinsaid continuous wave laser light is an argon laser light.
 54. A methodaccording to claim 44 wherein said semiconductor device is incorporatedinto one selected from the group consisting of personal computer, videocamera, mobile computer, head-mount display, player used for recordingmedium storing programs, digital camera, portable telephone, portablebook, and display.
 55. A method for forming a semiconductor devicecomprising: forming a semiconductor film over a substrate, saidsemiconductor film extending in a pixel region and a driver circuitregion; and irradiating a continuous wave laser light to a part of saidsemiconductor film in at least said driver circuit region while movingsaid substrate relative to said continuous wave laser light tocrystallize said part of said semiconductor film in at least said drivercircuit region, while a part of the semiconductor film in said pixelregion is not irradiated with said continuous laser light.
 56. A methodaccording to claim 55 wherein an active layer of an N-channel thin filmtransistor of said driver circuit region is formed in the crystallizedpart of said semiconductor film.
 57. A method according to claim 55wherein an active layer of a P-channel thin film transistor of saiddriver circuit region is formed in the crystallized part of saidsemiconductor film.
 58. A method according to claim 56 wherein saidactive layer comprises a source region, a drain region, a channel regionand a lightly doped drain region.
 59. A method according to claim 57wherein said active layer comprises a source region, a drain region, achannel region and a lightly doped drain region.
 60. A method accordingto claim 55 wherein a shift register circuit is formed in said drivercircuit region.
 61. A method according to claim 55 wherein a levelshifter circuit is formed in said driver circuit region.
 62. A methodaccording to claim 55 wherein a buffer circuit is formed in said drivercircuit region.
 63. A method according to claim 55 wherein a samplingcircuit is formed in said driver circuit region.
 64. A method accordingto claim 55 wherein said continuous wave laser light is an argon laserlight.
 65. A method according to claim 55 wherein said semiconductordevice is incorporated into one selected from the group consisting ofpersonal computer, video camera, mobile computer, head-mount display,player used for recording medium storing programs, digital camera,portable telephone, portable book, and display.
 66. A method for formingan electroluminescent display device comprising: forming a semiconductorfilm over a substrate, said semiconductor film extending in a pixelregion and a driver circuit region; and irradiating a continuous wavelaser light to a part of said semiconductor film in at least said drivercircuit region to crystallize said part of said semiconductor film in atleast said driver circuit region while a part of the semiconductor filmin said pixel region is not irradiated with said continuous laser light.67. A method according to claim 66 wherein an active layer of anN-channel thin film transistor of said driver circuit region is formedin the crystallized part of said semiconductor film.
 68. A methodaccording to claim 66 wherein an active layer of a P-channel thin filmtransistor of said driver circuit region is formed in the crystallizedpart of said semiconductor film.
 69. A method according to claim 67wherein said active layer comprises a source region, a drain region, achannel region and a lightly doped drain region.
 70. A method accordingto claim 68 wherein said active layer comprises a source region, a drainregion, a channel region and a lightly doped drain region.
 71. A methodaccording to claim 66 wherein a shift register circuit is formed in saiddriver circuit region.
 72. A method according to claim 66 wherein alevel shifter circuit is formed in said driver circuit region.
 73. Amethod according to claim 66 wherein a buffer circuit is formed in saiddriver circuit region.
 74. A method according to claim 66 wherein asampling circuit is formed in said driver circuit region.
 75. A methodaccording to claim 66 wherein said continuous wave laser light is anargon laser light.
 76. A method according to claim 66 wherein saidelectroluminescent display device is incorporated into one selected fromthe group consisting of personal computer, video camera, mobilecomputer, head-mount display, player used for recording medium storingprograms, digital camera, portable telephone, and portable book.
 77. Amethod for forming a semiconductor device comprising: forming asemiconductor film over a substrate, said semiconductor film extendingin a pixel region and a driver circuit region; and irradiating acontinuous wave laser light to a part said semiconductor film in atleast said driver circuit region while moving said substrate relative tosaid continuous wave laser light to crystallize said part of saidsemiconductor film in at least said driver circuit region while a partof the semiconductor film in said pixel is not irradiated with saidcontinuous laser light by using a galvanometer.
 78. A method accordingto claim 77 wherein an active layer of an N-channel thin film transistorof said driver circuit region is formed in the crystallized part of saidsemiconductor film.
 79. A method according to claim 77 wherein an activelayer of a P-channel thin film transistor of said driver circuit regionis formed in the crystallized par of said semiconductor film.
 80. Amethod according to claim 78 wherein said active layer comprises asource region, a drain region, a channel region and a lightly dopeddrain region.
 81. A method according to claim 79 wherein said activelayer comprises a source region, a drain region, a channel region and alightly doped drain region.
 82. A method according to claim 77 wherein ashift register circuit is formed in said driver circuit region.
 83. Amethod according to claim 77 wherein a level shifter circuit is formedin said driver circuit region.
 84. A method according to claim 77wherein a buffer circuit is formed in said driver circuit region.
 85. Amethod according to claim 77 wherein a sampling circuit is formed insaid driver circuit region.
 86. A method according to claim 77 whereinsaid continuous wave laser light is an argon laser light.